The present invention generally relates to a frame for a metal-cutting saw of the one-piece hacksaw type including a bow extended at its rear end by a pistol grip. The pistol grip includes a hand-protection branch which meets the grip at the lower part, and which incorporates a blade-tensioning mechanism.
The user of a metal-cutting saw needs to change the blade of his tool either regularly, because the blade is becoming worn, or to change the type of blade depending on the specific type of cutting being done. All of these blade changes tend to make the blade tensioning increasingly less precise.
Metal-cutting saws having adjustable blade-tensioning devices have previously been proposed in order to solve this problem. For example, French Patent Application No. 2,624,780 discloses a device having a profiled lever with a cam shape which is capable of pushing up against and then tilting against the opposing face of the blade-holder arm. The lever is associated, via its lower part, with the outer end of a tension-retaining member, or fitting. The fitting allows the tension to be adjusted by altering the position of a nut provided on the fitting.
The disclosed device, which is relatively quick to operate, does not allow the blade to be adjusted very accurately because the position of the nut provided for achieving such adjustment can vary only by whole numbers of turns.
U.S. Pat. Nos. 4,367,779 and 4,466,471 also disclose metal-cutting saws with mechanisms for adjusting the tension of the blade using a lever in the hand grip of the saw which pivots to create tension in the blade through a rod which acts on a lever arm. In each case, the tension is adjusted by varying the length of the rod.
Although generally satisfactory, such devices are on the one hand complicated to operate, while on the other hand, because of their significant number of component parts, such devices are not very robust from a mechanical point of view.
Accordingly, it is an object of the present invention to overcome the drawbacks of these prior devices while allowing the user to preset the tension in the saw blade.
Another object of the present invention is to allow the blade to be fitted quickly, by limiting the number of operations to be carried out on the frame.